High-sensitivity polarization gating frequency-resolved optical gating (PG-FROG) using highly-nonlinear dispersion-shifted fiber

We experimentally demonstrate a frequency-resolved optical gating (FROG) system in pulse characterization at 1.55 μm by using cross-phase modulation (XPM) in highly nonlinear dispersion-shifted fiber (HNL-DSF), with over 6-times sensitivity improvement. © 2011 National Sun Yat-Sen Univ.published_or_final_versio

Comparison of the state-of-art phase modulators and parametric mixers in time-lens applications under different repetition rates

Ever since the discovery of space-time duality, several methods have been developed to perform temporal imaging, and there are two major categories: the quadratic signal onto the phase modulator and the parametric mixer with a linear chirped pump. The features of each mechanism have been thoroughly and quantitatively explored and optimized for certain kinds of applications, but a comparison of some key parameters, especially in the aspect of the repetition rate, is required. In this paper, we will first review the theoretical models and existing performance of these two mechanisms and, consequently, compare them quantitatively in different aspects: the focal group delay dispersion, the pupil size, the effective duty ratio, and the temporal numerical aperture. All these fundamental parameters are related to the repetition rate. The results obtained in this study would provide some important guidelines for the time-lens design, so as to be optimized in different kinds of applications with different repetition rate requirements, such as ultrafast optical communication and real-time bio-imaging systems.published_or_final_versio

Rapid turnover of effector-memory CD4(+) T cells in healthy humans

Memory T cells can be divided into central-memory (T(CM)) and effector-memory (T(EM)) cells, which differ in their functional properties. Although both subpopulations can persist long term, it is not known whether they are maintained by similar mechanisms. We used in vivo labeling with deuterated glucose to measure the turnover of CD4(+) T cells in healthy humans. The CD45R0(+)CCR7(-) T(EM) subpopulation was shown to have a rapid proliferation rate of 4.7% per day compared with 1.5% per day for CD45R0(+)CCR7(+) T(CM) cells; these values are equivalent to average intermitotic (doubling) times of 15 and 48 d, respectively. In contrast, the CD45RA(+)CCR7(+) naive CD4(+) T cell population was found to be much longer lived, being labeled at a rate of only 0.2% per day (corresponding to an intermitotic time of approximately 1 yr). These data indicate that human CD4(+) T(EM) cells constitute a short-lived cell population that requires continuous replenishment in vivo

A tunable S-plus L-band continuous-wave single-longitudinal-mode fiber-optical parametric oscillator

We demonstrate an all-fiber continuous-wave single-longitudinal-mode fiber-optical parametric oscillator. The output tuning range extends from 1487 to 1541 nm and from 1570 to 1630 nm, which covers the S- and L-bands. Single-longitudinal-mode oscillation with a side-mode suppression ratio greater than 43 dB is achieved while the linewidth of the output is 1.5 kHz. This scheme has the potential to be a useful source in wavelength-division-multiplexing networks and optical communications in the nonconventional wavelength bands. © 2011 IEEE.published_or_final_versio

Forensically informative nucleotide sequencing (FINS) for the authentication of Chinese medicinal materials

Chinese medicinal materials may be authenticated by molecular identification. As a definitive approach to molecular identification of medicinal materials, forensically informative nucleotide sequencing (FINS) comprises four steps, namely (1) DNA extraction from biological samples, (2) selection and amplification of a specific DNA fragment, (3) determination of the sequence of the amplified DNA fragment and (4) cladistic analysis of the sample DNA sequence against a DNA database. Success of the FINS identification depends on the selection of DNA region and reference species. This article describes the techniques and applications of FINS for authenticating Chinese medicinal materials. © 2011 Li et al; licensee BioMed Central Ltd.published_or_final_versio

Large area laser scanning optical resolution photoacoustic microscopy using a fibre optic sensor

A laser scanning optical resolution photoacoustic microscopy (LS OR-PAM) system based on a stationary fibre optic sensor is described. The sensor comprises an optically resonant interferometric polymer cavity formed on the tip of a rounded single mode optical fibre. It provides low noise equivalent pressure (NEP = 68.7 Pa over a 20 MHz measurement bandwidth), a broad bandwidth that extends to 80 MHz and a near omnidirectional response. The latter is a significant advantage, as it allows large areas ( > 1cm 2 ) to be imaged without the need for translational mechanical scanning offering the potential for fast image acquisition. The system provides a lateral resolution of 8 µm, an axial resolution of 21 µm, and a field of view up to 10 mm × 10 mm. To demonstrate the system, in vivo 3D structural images of the microvasculature of a mouse ear were obtained, showing single capillaries overlaying larger vessels as well as functional images revealing blood oxygen saturation

All-optical endoscopic probe for high resolution 3D photoacoustic tomography

A novel all-optical forward-viewing photoacoustic probe using a flexible coherent fibre-optic bundle and a Fabry- Perot (FP) ultrasound sensor has been developed. The fibre bundle, along with the FP sensor at its distal end, synthesizes a high density 2D array of wideband ultrasound detectors. Photoacoustic waves arriving at the sensor are spatially mapped by optically scanning the proximal end face of the bundle in 2D with a CW wavelength-tunable interrogation laser. 3D images are formed from the detected signals using a time-reversal image reconstruction algorithm. The system has been characterized in terms of its PSF, noise-equivalent pressure and field of view. Finally, the high resolution 3D imaging capability has been demonstrated using arbitrary shaped phantoms and duck embryo

Mixup for Test-Time Training

Test-time training provides a new approach solving the problem of domain shift. In its framework, a test-time training phase is inserted between training phase and test phase. During test-time training phase, usually parts of the model are updated with test sample(s). Then the updated model will be used in the test phase. However, utilizing test samples for test-time training has some limitations. Firstly, it will lead to overfitting to the test-time procedure thus hurt the performance on the main task. Besides, updating part of the model without changing other parts will induce a mismatch problem. Thus it is hard to perform better on the main task. To relieve above problems, we propose to use mixup in test-time training (MixTTT) which controls the change of model's parameters as well as completing the test-time procedure. We theoretically show its contribution in alleviating the mismatch problem of updated part and static part for the main task as a specific regularization effect for test-time training. MixTTT can be used as an add-on module in general test-time training based methods to further improve their performance. Experimental results show the effectiveness of our method.Comment: 11 page